Lance Taylor
Jessi Hartman
Adam Flournoy
ENGR 45,
SRJC,
Fall 2013
Richmond Refinery Fire August 2012
 The destruction of a material by a chemical or
electrochemical process through interaction with its
environment.
 Typically this is a transfer of electrons from one metal
to another which is an oxidation-reduction reaction.
 The corrosion of a metal is a chemical process by
which the metal is oxidized.
 Normal rain water has a slightly acidic pH of 5.6.
 Acid rain has a typical value of 4.3.
 Acid rain not only affects the health of the
environment but also the health of materials and
alloys.
 There are 8 common forms of corrosion:
 Uniform (rust)
 Galvanic
 Crevice
 Pitting
 Intergranular
 Selective Leaching
 Erosion-Corrosion
 Stress Corrosion
Most common form of corrosion
Oxidation-Reduction reactions occur
randomly over entire exposed surface
Magnesium Shell
 Occurs when two metals or alloys with
dissimilar compositions are electrically
coupled while exposed to the same
electrolyte.
 Typically in marine environments.
 The more inert metal is protected from
corrosion while the more reactive metal
will degrade.
Galvanic Corrosion
Steel Core
Crevice
Pitting
 Both are forms of localized corrosion.
 Occur from concentration differences of ions
forming a concentration cell.
 Oxidation occurs within the pit or space between
two metals.
 Insidious form of corrosion because it can go
undetected with little material loss until failure
occurs.
 Corrosion occurs
preferentially along grain
boundaries for some alloys
in specific environments.
 Also known as weld decay.
 Specific to stainless steels
where heat treatment
allows the formation of
small precipitate particles
that form along grain
boundaries.
 This leaves a chromium
depleted zone that is
highly susceptible to
corrosion.
• Occurs when one element is
preferentially removed from an
alloy during the corrosion process.
• This leaves behind a porous and
weak material susceptible to failure.
• Example: The dezincification of
Brass. Zinc is selectively leached from
the alloy and leaves behind the
reddish copper in the region
bereft of Zinc.
 Occurs because of
chemical reactions
combined with
mechanical wear
from abrasive fluids
in motion.
 Commonly found in
pipes and especially
around bends and
elbows or where
there are changes in
pipe diameter.
 Increased fluid
velocity = increased
corrosion rate.
Erosion
Example: Richmond Refinery!
 Cracks grow
perpendicular
to grain
boundaries
because of
applied tensile
stresses
combined with
a corrosive
environment.
Stress Crack
 Our goal was to simulate the effect of acid rain, a
uniform corrosion, on various metals and alloys
commonly used for building and tool materials.
 The experiment was conducted within a temperature
range of 50 to 70 degrees degrees Fahrenheit.
 A plastic non-reactive tank was used for the control
environment.
 0.01 M Sulfuric Acid was used to simulate the corrosive
environment; about 100x stronger than normal acid
rain.
Samples used for Acid Rain simulation
Zinc
Monel
Copper Steel Aluminum
Brass
Failure during
cold working
Stainless
Steel
Annealed Stainless Steel
Stainless Steel touching Monel Steel
Annealed Stainless Steel
Stainless Steel touching Monel Steel
Annealed Stainless Steel
Stainless Steel touching Monel Steel
Annealed Stainless Steel
Stainless Steel touching Monel Steel
Effects of CW on Hardness
120
100
Rockwell Hardness B
80
60
40
Cold Worked
20
Not Cold Worked
0
1
2
3
4
5
6
-20
-40
-60
1 – Copper
2 – Aluminum
3 – Stainless Steel
4 – Brass
5 – Monel Steel
6 – Zinc
“Effect of cold‐work on corrosion of metals in general is
greatest when a second phase precipitates to form active
galvanic cells, whereas the increase in internal energy of a
disarrayed metal lattice has little if any effect. Preferred grain
orientation of surface metal sometimes resulting from
cold‐work may either increase or decrease corrosion.”(3)
 No measurable difference in loss of mass. Scales used were




not able to measure difference in pre and post weights of
metal samples.
No difference in hardness after 3 weeks corrosion testing.
Samples did not have enough time to sufficiently degrade.
Corrosion of unannealed stainless steel possibly through
galvanic corrosion.
Corrosion of aluminum not cold worked possibly from
crevice corrosion. Sample was laid flat on the bottom of
the tank.
No effect of corrosion on hardness before and after
corrosion testing.
Sacrificial Anode
 Several measures may be taken to prevent, or at
least reduce, corrosion. These include material
selection, environmental alteration, the use of
inhibitors, design changes, application of coatings,
and cathodic protection.
 Surface coatings can also be used to prevent corrosion
 Painting, plating and anondizing metals can limit the
amount of surface area susceptible to corrosion.
 Some materials such as aluminum and stainless steel
form oxide barriers that prevent oxidation at the surface
Oxidation-Reduction
reaction without an
oxide barrier or
surface coating
 Choose corrosion resistant materials
 Prevent accumulation of water, salts, gasses within
structures
 Inspect C.C.P. (Critical Control Points) regularly with
non-destructive techniques.
Don’t let this happen to you!
 1 - Callister, Jr., William D. and David G. Rethwisch
Materials Science and Engineering: An Introduction.
Eighth ed. USA: Wiley, 2010. Print.
 2 - Serway, Raymond A., and John W. Jewett, Jr. Physics
for Scientists and Engineers. Eigth ed. Belmont:
Brooks/Cole, 2010. Print.
 3 – Journal of the Electrochemical Society
 http://jes.ecsdl.org/content/111/5/522.abstract
 Certain images used courtesy of open internet domain